Cellulosic material and process for preparing same



Patented May 23, 1939 CELLULOSIO MATERIAL AND PROCESS FOR PREPARING SAMEAmbrose W. Staudt, Kenmore, N. Y., assignor, by mesne assignments, to E.L du Pont de Nemours & Company, Wilmington, Del., a corporation ofDelaware No Drawing. Application March 23. 1936, Serial No. 70,401

11 Claims.

This invention relates to the application of labels to various articlesand more particularly to a method of afiixing the usual gummed labels tothin sheets or films suitable for use as wrapping tissues, includingcellulose derivative films such as those of cellulose acetate, cellulosenitrate, cellulose ethers, or the like.

Labels are aflixed to articles and packages of all kinds for variousreasons. The usual labels are treated with an adhesive such as glue,dextrine and the like, of such a character that when they are to beafflxed to an article it is only necessary to moisten the adhesivesurface and apply the label to the article. The usual labels areprovided with an adhesive which is of a water soluble type, or one whichis capable of becoming energized by the application of water. With theadvent of cellulose derivative wrapping tissues, such as those ofcellulose acetate, it has been impossible to afilx the usual gummedlabels to such wrapping tissues, in the sealing, closing, labelling orthe like of packages wrapped therein because the water energizedadhesive will not stick to the cellulose derivative and a firmand usefulbond cannot be obtained. Of course, a special gumming composition mightbe applied to the label which could be energized by some material whichwould simultaneously modify thecellulose derivative wrapping tissue andenable a firm bond to be obtained. This would require, however, that aseparate supply of labels be on hand for each type of cellulosederivative wrapping tissue and the label manufacturer would be put tothe serious inconvenience of having to carry a stock of labels providedwith a variety of adhesives, depending on the requirements of a largenumber of customers. The present invention provides means whereby labelsgummed with the usual, water energizable adhesives can be firmly andpermanently afiixed to cellulose derivative wrapping tissues.

It has been proposed previously (Snyder United States 1,815,365) toailix gummed labels of the usual type to articles made from or having acoating including a cellulose derivative, such as cellulose acetate,cellulose nitrate, cellulose ethers or the like, by moistening thegummed label with a liquid composition comprising in its preferred forma material capable of rendering the adhesive on the label tacky and alsoa solvent or softener for the cellulose derivative. Thus, a solutioncomprising a mixture of water and ethylene glycol monomethyl ether mightbe used.

The moistening solution described by Snyder is particularly useful inthe aflixing of gummedlabels to regenerated cellulose film coated withcellulose derivative compositions because the solvent in the moisteningsolution modifies only the cellulose derivative coating and theregenerated cellulose base is capable of maintaining the integrity ofthefilm until after the solvent has evaporated. In the application ofgummed labels to self-sustaining films of cellulose derivatives andparticularly those which are sufliciently thin to serve as wrappingtissues, considerable care must be taken to avoid such an attack on thecellulose derivative by the solvent in that the film will be distorted,wrinkled or even .completely destroyed.

The present invention provides an improved moistening solution and animproved method for aflixing gummed labels to self-sustaining sheets orfilms of cellulose derivatives, particularly cellulose acetate, whichare suitable for use as wrapping tissues.

It is therefore an object of this invention to provide an improvedmethod of affixing gummed labels to cellulose derivative wrappingtissue, the bond between the label and the wrapping tissue being strongand permanent and effected without curling, wrinkling, buckling ordestruction of the wrapping tissue involved.

Generally speaking, the objects of the invention are accomplished bymeans of a moistening solution comprising a cellulose derivative, 9.softener for the label gumming material and a solvent or mixture ofsolvents, with or without a plasticizer for the cellulose derivative,and preferably though not necessarily containing an appreciable quantityof water. In its preferred embodiment the invention contemplates the useof a moistening solution comprising a cellulose derivative in minorproportion, a plasticizer for that cellulose derivative also in minorproportion, and a-softener for the label gumming material in majorproportion dissolved in a solvent or mixture of solvents containing upto 40% water.

The cellulose derivative and the softener for the label gumming materialare essential in these moistening solutions for the development of afirm, permanentbond between the label and the cellulose derivativematerial which is used as the wrapper. The preferred modification of themoistening solution includes water in the solvent mixture since by thepresence of water, it is possible to secure a quick, initial tackinessso that the labels can be made to adhere immediately after moisteningwithout being held in place while the solvents are permitted to dry.

The cellulose derivatives which are useful in the practice of thisinvention includes cellulose acetate, cellulose nitrate, cellulosepropionate, cellulose butyrate, cellulose aceto-propionate, ethylcellulose, benzyl cellulose or other cellulose esters or ethers. Whenusing cellulose acetate, an acetone soluble variety having a very lowviscosity is preferable. This material usually contains between 42 and58% combined acetic acid and the viscosity may be made quite low by anyof the methods known to the art, either by the direct production of alow viscosity cellulose acetate or by reduction of the viscosity of apreviously prepared, dried cellulose acetate flake. A low viscositycellulose acetate obtained by the treatment of cellulose acetate flakewith dry hydrochloric acid gas as described in Reid United States PatentNo. 1,874,350 has been used successfully in the practice of the presentinvention.

Those cellulose derivatives which exhibit a fairly high tolerance forwater are particularly useful in the practice of the invention inasmuchas the preferred moistening solutions contain fairly large proportionsof water. Thus, cellulose acetate with a low acetyl content has agreater tolerance for water in acetone-water mixtures than does a highlyacetylated product, so that it is particularly adaptable to thepreparation of moistening solutions containing a high percentage ofwater in the solvent mixture and by-means of which good initialtackiness can be secured. When nitrocellulose is used, it is preferableto employ the ethyl alcohol soluble type or other low viscosity typespossessing a high tolerance for water. The low viscosity solutions arepreferred inasmuch as they lend themselves much more readily to use instandard equipment which generally involves application of a moisteningsolution by means of wicks or brushes.

The softener for the label gumming material is chosen from among suchsubstances as glycerol,

ethylene glycol, monoethylin (glycerol monoethyl ether), mono-acetln(glycerol mono-acetic acid ester), acetamide, heptyl alcohol, glycerolmonolactate,polyglycerols,polyglycols and the like. The softener isusually one which will cause the gum to remain soft and prevent it fromshrinking too much after the water or other solvent has evaporated.Generally, a rather high proportion of this ingredient is essential inaffixing labels to thin sheets of cellulose acetate, for example, inorder to avoid as much as possible any wrinkling or distortion whichwould mar the appearance of the package. Preferably, a softener will bechosen, which in addition to being a softener for the gumming materialon the label will also tend to have a softening or plasticizing effecton the cellulose derivative sheet material. Monoethylin and mono-acetinare good examples of such compounds.

Mention has been made of the alternative use of a cellulose derivativeplasticlzer to plasticize the cellulose derivative in the moisteningsolution. Where such a plasticizer is desired, its choice willdepend-largely on the cellulose derivative and the following substancesmay be used singly or in combination with themselves or other cellulosederivative plasticizers:

The solvents used in the preparation of these moistening solutionsshould be chosen so as to produce clear, low viscosity solutions. Theyshould be highly volatile so that they will dry out of the joint quicklyafter the moistened label has been aflixed to the desired surface. Thesolvents or solvent mixture should be of such nature that they will notcause excessive wrinkling, shrinkage or other distortion of thecellulose derivative wrapping tissue to which the label is afllxed.Representative solvents are disclosed in the accompanying, illustrativeexamples.

As mentioned above, it is preferable to employ water in the solventmixtures and as much as 40% water can be used, depending on the type ofcellulose derivative and the choice of organic "solvents. In someinstances more than 40% water can be employed; Although the water is notessential for the permanent bonding of the labels to the cellulosederivative surface, it is preferred a for the development of quick,initial tackiness of the label gumming material so that the labels willadhere to the surface immediately after being placed thereon and willnot require need for holding them in position until the solvents havedried. Usually, the water also tends to decrease the activity of thesolvents towards the cellulose derivative sheet material and thusassists in avoiding undue wrinkling, shrinkage or other distortion ofthe sheet.

It is also preferred that the water he used in an amount which willdissolve in the organic solvents present since the preferred moisteningcompositions, including those of the examples given .below, arehomogeneous mixtures or solutions.

The following specific examples are illustrative of typical moisteningsolutions, prepared in accordance with the present invention. By meansof these moistening solutions labels gummed with the usual adhesivessuch as gelatin, dextrin, fish glue, acacia gum or the like may befirmly and permanently ailixed to thin sheets of cellulose derivatives,such as cellulose acetate wrapping tissue.

Example I Per cent Cellulose acetate (low viscosity) 4 Methoxyethylphthalate 4 Monoethylin 30 Acetone- 46 Water '16 Example II Per centToluol Water Example III Per cent Cellulose acetate (containing 44%combined acetic acid, low viscosity type) 2 Triacetin Glycerol Ar-efnneExample IV Per cent Nitrocellulose (low viscosity ethyl alcohol solubletype) Diethyl phthalate 2 Monoacetin 10 Ethyl alcohol 68 Toluol 8 Water10 Example V Per cent Cellulose acetate (containing 44% combined '(Note:The alcohol of this example contained about 10% acetone.)

In practicing the invention the gumming material on the gummed label ismoistened with a moistening solution, whereupon the label is applied tothe sheet of cellulose derivative wrapping tissue and the solvents arepermitted to evaporate either by air drying or forced drying, such as bythe application of heat. Suflicient pressure is usually employed to holdthe label against the surface of the wrapping tissue.

Moistening solutions prepared in accordance with this invention arenon-viscous and nonstringing, so that they may be applied to the gummedlabel quickly and easily by hand or machine operation. These solutionsand the constituents thereof may be removed from the hands of operatorsor machine parts simply by washing with water. The-moistening solutionsyield residues which are odorless after drying and when dry, thenon-volatile constituents of the solutions are transparent, so thattransparent gummed labels may be aflixed without obliterating printedmatter or decorative designs that may be under or on the sheeting towhich the label is amxed.

The invention has been described in connection with the application ofgummed labels to cellulose acetate wrapping tissue. It will beunderstood, however, that these moistening solutions can be used equallywell to aflix gummed labels to thin sheets of nitrocellulose or othercellulose derivative sheeting, to transparent sheet-,

ing or other objects coated with cellulose acetate, cellulose nitrate orother cellulose derivative lacquers including those cellulose derivativelacquers which contain wax or other moistureprooflng agent and likewiseto cellulose derivative plastic or molded objects. Gummed labelsmoistened with these solutions and affixed to a cellulose derivativesheet, object or coating may be used for labelling to identify oradvertise by means of printed or written message or notation on thelabels, or they may be used to close the package by holding the foldedends or edges of the cellulose derivative wrapping tissue or thecellulose derivative coated sheeting. The labels may be of paper, clothor any other materials commonly 'used for labelling, instructing orsealing pack- .ages.

Parts and proportions given above are parts and proportions by weightunless otherwise specified.

As many widely different embodiments of the invention are possible, theinvention is not to be limited to the above specific description andexamples except as indicated in the claims.

I claim:

1. An article comprising, in combination, a body having a surfaceconsisting of a cellulose derivative, a body having a surface consistingof a water-energizable adhesive, said two surfaces of said bodies bondedto each other by means of an agent therebetween, said agent comprising,as the sole adhesion-inducing ingredients, a cellulose derivative and asoftener for said water-energizable adhesive.

2. An article comprising, in combination, a thin flexible sheet having asurface consisting of a cellulose derivative, a label having a surfaceconsisting of a water-energizable adhesive, said two surfaces of saidtwo elements bonded to each other by means of an agent therebetween,said agent comprising, as the sole adhesion-inducing ingredients, acellulose derivative and a softener for said water-energizable adhesive.

3. An article comprising, in combination, a thin, flexible, cellulosederivative sheet, a label having a surface'consisting of awater-energizable adhesive, said surface of said label bonded to saidcellulose derivative sheet by means of an agent therebetween, said agentcomprising, as the sole adhesion-inducing ingredients, a cellulosederivative and a softener for said water-energizable adhesive.

4. An article comprising, in combination, a thin, flexible, celluloseacetate sheet, a label having a surface consisting of awater-energizable adhesive, said surface of said label bonded to saidcellulose acetate sheet by means of an agent therebetween, said agentcomprising, as the sole adhesion-inducing ingredients, a cellulosederivative and a softener for said water-energizable adhesive.

5. The method of aiiixing to a cellulose derivative surface of a body awater-energizable adhesive surface of a second body which comprisesapplying between said cellulose derivative surface and said adhesivesurface of said two bodies a liquid composition containing in solution,as the sole adhesion-inducing ingredients, a cellulose derivative and asoftener for said adhesive.

6. The method of affixing to a cellulose derivative surface of a thinflexible sheet a water-energizable adhesive surface of a label whichcomprises applying between said cellulose derivative.

surface and said adhesive surface of said two elements a liquidcomposition containing in solution, as the sole adhesion-inducingingredients, a cellulose derivative and a softener for said adhesive.

7. The method of aflixing to a cellulose derivative surface of a thinflexible sheet a water-energizable adhesive surface of a label whichcomprises applying between said cellulose derivative surface and saidadhesive surface of said two elements a liquid composition containing insolution, a cellulose derivative, a plasticizer for said derivative, asoftener for said adhesive. and water; said cellulose derivative andsaid softener being the sole adhesion-inducing ingredients of saidcomposition.

8. The method of affixing to a thin, flexible, cellulose derivativesheet. a water-energizable adhesive surface of a label which com risesapplying between said water-energizable adhesive surface of said labeland said sheet a liquid composition containing a cellulose derivative. aplasticizer for said derivative, a softener for said adhesive, andwater, said cellulose derivative and said softener being the soleadhesion-inducing ingradients of said composition.

9. A composition suitable for adhering the cellulose derivative surfaceof a body to the waterenergizable adhesive surface of a second body,said composition comprising a cellulose derivative, a solvent for saidcellulose derivative, and a softener for said water-energizableadhesive, said cellulose derivative and said softener being the soleadhesion-inducing ingredients of said composition.

10. A composition suitable for adhering the cellulose derivative surfaceof a body to the waterenergizable adhesive surface of a second body,said composition comprising a cellulose derivative, a solvent and aplasticizer for said cellulose derivative, a softener for saidwater-energizable adhesive and water, said cellulose derivative and saidsoftener being the sole adhesion-inducing ingredients of saidcomposition.

11. A composition suitable for adhering the cellulose derivative surfaceof a body to the waterenergizable adhesive surface of a second body,said composition comprising a homogeneous mixture containing a cellulosederivative, a solvent and a, plasticizer for. said cellulose derivative,a softener for said water-energizable adhesive and water, said cellulosederivative and said softener being the sole adhesion-inducingingredients of said composition.

AMBROSE W. STAUDT.

